Valve assemblies for controllably diverting the flow of fluids are well known which include a supply port, a control port, and a vent port. In general terms, the supply port receives fluid from a fluid source while a valve member within the valve assembly is moved into and out of contact with a valve seat. When the valve member is seated with the valve seat, communication between the supply port and the control port is permitted and communication between the control port and the vent port is prevented. In this way, fluid is received at the working at a relatively high pressure. Conversely, when the valve member is not seated with the valve seat, communication between the control port and the vent port is permitted, thereby causing the pressure at the control port to decrease. Also when the valve member is not seated with the valve seat, communication between the supply port and the control port is often prevented. An example of such a valve assembly is shown in U.S. Pat. No. 9,016,663 to Moreno et al., hereinafter referred to as Moreno et al.
A common usage for valve assemblies such as those disclosed by Moreno et al. is to variably actuate engine control subsystems such as multi-step or valve deactivation mechanisms for valve train which is responsible for opening and closing combustion valves which allow combustion constituents into combustion chambers and which allow exhaust constituents out of the combustion chambers of an internal combustion engine. These multi-step or valve deactivation mechanisms, hereinafter referred to as working devices, switch between a first mode of operation and a second mode of operation at a predetermined pressure of fluid supplied thereto by the valve assembly where one such working device is described, by way of non-limiting example only, in United States Patent Application Publication No. 2015/0345343 A1 to Lee et al., hereinafter referred to as Lee et al. In a first mode of operation of the working device of Lee et al., a high lift follower is used to open and close a combustion valve to a first magnitude. Conversely, in a second mode of operation when high pressure oil is supplied to the working device of Lee et al., a pair of low lift followers are used to open and close the combustion valve to a second magnitude that is less that the first magnitude provided by the high lift follower.
While many different port configurations of valve assemblies are known, it is most prominent to have the control port located at a location that is axially between the vent port and the supply port as shown in Moreno et al. or to have the supply port located at a location that is axially between the vent port and the control port as shown in U.S. Pat. No. 8,746,279 to Muzquiz et al., herein after referred to as Muzquiz et al. While valve assemblies such as those described by Moreno et al. and Muzquiz et al. may be satisfactory in the environments for which they are intended, some environments may require the vent port to be located at a location that is axially between the control port and the supply port. Furthermore, it may be desirable to allow fluid to be supplied to the control port at a reduced pressure at the control port even when the valve member is positioned to prevent high pressure at the control port. However, providing a valve assembly with the vent port located at a location that is axially between the control port and the supply port and also which allows fluid to be supplied to the control port at a reduced pressure at the control port even when the valve member is positioned to prevent high pressure at the control port may be difficult to implement.
What is needed is a valve assembly which minimizes or eliminates one or more the shortcomings as set forth above.